Science & Justice最新文献

Isotopic analysis of human tooth enamel can provide life history information useful in forensic identification. These applications depend on the availability of reference data documenting isotopic values for individuals with known life history and on the comparability of data from reference and case work samples. Here we build on previous methodological research, which has largely focused on paleontological and archaeological samples, and conduct experiments using enamel from modern human teeth targeting three sample preparation variables (sample particle size, storage conditions, and chemical pretreatments). Our results suggest that differences in particle size affect the efficiency of sample reactions during pretreatment and analysis, with coarse particles giving reduced loss of enamel carbonate during acid pretreatments but producing slightly higher oxygen isotope values than fine particles during analysis. Data for samples stored in dry and ambient environments following pretreatment were indistinguishable, suggesting no exchange of oxygen between samples and ambient water vapor. Finally, chemical pretreatments with a range of commonly used reactants and conditions showed a pervasive, moderate oxygen isotope shift associated with acetic acid treatment, which may be caused by exchange of enamel hydroxyl groups with reagents or rinse waters. Collectively, the results emphasize the importance of methodological standardization to improve comparability and reduce potential for bias in the forensic application of tooth enamel isotope data.

The serial character of document fraud and its connection to organised crime groups who produce, sell and/or use fraudulent documents is a challenge for security and crime fighting. As a response, the added value of forensic intelligence is increasingly recognised. Using a forensic profiling method and a dedicated system deployed in Switzerland, document examiners can detect series (i.e., documents that share a common source) of fraudulent documents conveniently and efficiently. This detection can trigger or orientate investigations, supports crime intelligence efforts, and facilitates cross-jurisdictional cooperation. This study aims to assess the suitability of the forensic profiling system for international purpose and the efficiency of the method to detect cross-border series. The forensic profiling system has been deployed in France in the framework of a cross-border pilot project conducted by the School of Criminal Justice from the University of Lausanne and the French National Police (Division Nationale de Lutte contre la Fraude Documentaire et à l'Identité) over the period July 2019–May 2020. Data from the Swiss and French forensic profiling systems were compared to each other to detect cross-border series. The study sought to create operating conditions as close as possible to the real-life conditions of the profiling systems. The results are extremely positive both quantitatively and qualitatively. They demonstrate the benefit of setting up a systematic exchange of forensic data issued from profiling systems for fraudulent identity documents between France and Switzerland, let alone between any other countries. The results open up a very promising prospect for a sustained operational implementation by the police services of both countries and the extension of the exchanges internationally.

An eight year old boy was badly injured by a fire in his bedroom in May 2005. He spent his ninth birthday in intensive care and died a month later. This case study discusses a missing link into the pattern of fire development which made it difficult to identify the point of ignition. An absence of burning to the floor and isolated areas of burning seemed incongruous with the general pattern of fire development. Several fire investigation texts suggest that carpet cannot spread fire by itself; those texts that do mention the possibility, do not describe the mechanism in detail, nor what evidence an investigator might expect to see after the fire.

Experimentation with samples of carpet gave good insight into the mechanism and its effects, thereby providing the missing link by which to connect the areas of burning and identify the point of origin. If elements of the mechanism described in this paper are known, a reader could discern enough from the many papers available to support a working hypothesis but as yet, there is no single paper that describes the phenomenon mechanistically from start to finish, especially to those who have not encountered elements of it before; hence, this paper presents some novel findings.

The test involved polypropylene fibre carpets with integral polyurethane foam underlay, a very common type of carpet owing to its low cost and high durability. This is, therefore, an important mechanism of fire spread for fire investigators to be aware of and to understand. As this is a case study, rather than a research paper, the matters are dealt with empirically so the author cautions that when considering this mechanism in a new matter, the investigator should make their own tests of its validity.

If Y-STR profiling is to be more effective in criminal casework, the methods used to evaluate evidential weight require improvement. Many forensic scientists assign an evidential weight by estimating the number of times a Y-STR profile obtained from a questioned sample has been observed in YHRD datasets. More sophisticated models have been suggested but not yet implemented into routine casework, e.g. Andersen & Balding [1]. Mutation is inherent to STR meiosis (or inheritance) and is encountered in practice. We evaluated a mutation model that can be incorporated into a method for assigning evidential weight to Y-STR profiles, an essential part of bringing any method into practice. Since an important part of implementation to casework is communication, the article is written in an accessible format for practitioners as well as statisticians.

The mutation component within the MUTEA model by Willems et al. [2] incorporates the potential for multistep mutations and a tendency for alleles to revert towards a central length, reflecting observed mutation data, e.g. [3]. We have estimated the parameters in this model and in a simplified symmetric version of this model, using sequence data from father/son pairs [4] and deep-rooted pedigrees [5]. Both datasets contain multistep mutations, which may have an effect on models based on simulations [1].

We introduce Beta-Binomial and Beta-Geometric conjugate analyses for estimating rate and step parameters for the mutation models presented here, which require only summations and multiplications. We proved mathematically that the parameters can be estimated independently. We show the importance of reporting the variability of the parameters and not only a point estimate. The parameters can be easily incorporated into statistical models, and updated sequentially as more data becomes available. We recommend fuller publication of data to enable the development and evaluation of a wider range of mutation models.

The aim of this study was to estimate random match frequency of randomly acquired characteristics (RAC-RMF) for laboratory-simulated crime scene impressions. Part I of this investigation reports this metric using a dataset of more than 160 questioned impressions created in blood and deposited on tile. A total of 759 RACs were identified in the blood impressions and compared to RACs with positional similarity in test impressions from 1,299 unrelated outsoles. Geometric similarity was quantified using a combination of visual comparisons and mathematical modeling based on percent area overlap. Results indicated that RACs in blood impressions were typically smaller, and therefore exhibited a two-thirds increase in the number of indistinguishable pairs compared to their mated test impressions. For shoes contributing at least one RAC, relative RAC-RMF values $⩾$ 0.0008 were encountered at a rate between 3.4% and 34% for the blood impressions examined in this study. Part II of this investigation provides analogous results based on dust impressions deposited on paper and tile. Although the results in Part I and Part II are specific to randomly acquired characteristics and do not translate into an impression-wide RMF estimate, this research shows that RACs in questioned impressions of the type expected in casework co-occur in position and geometry with RACs in non-mated test impressions. Since theoretical models have traditionally been the basis for estimating RAC-RMF in footwear, the overall contribution of this research to the forensic footwear community is a calibration of this estimate based on empirical data.

This study serves as Part II of an investigation into the random match frequency of randomly acquired characteristics (RAC-RMF) in footwear evidence. In Part I, RAC-RMF was estimated in a dataset of laboratory-simulated crime scene impressions deposited in blood. For Part II, a second dataset was created composed of impressions deposited in dust on paper or tile, with the latter lifted using gelatin or Mylar film. A total of 1,513 RACs were identified from more than 160 dust impressions and compared to RACs with positional similarity in test impressions from 1,299 non-mated outsoles. RACs of any size deposited in dust exhibited a 31% decrease in shoes with non-zero RAC-RMFs as compared to their mated test impressions, while those deposited in blood exhibited a 45% increase. When only considering shoes with at least one RAC deemed forensically-reliable (length $⩾$ 2.8 mm), 3.1% of shoes contributing dust impressions and 3.4% of shoes contributing blood impressions exhibited relative RAC-RMFs at a value $⩾$ 0.0008. Although each dataset resulted in a comparable rate for encountering non-zero RAC-RMFs, the estimate for dust was based on twice the number of RAC comparisons (154,477) than those performed when assessing blood (77,566). While these results are considered specific to the non-mated impressions and methods of analysis described herein, and continued work is required before rates can be fully understood and reported in forensic casework, this study encountered non-zero RAC-RMFs for shoes exhibiting at least one forensically-reliable RAC at a more frequent rate than any estimates previously reported.

The illicit exploitation of Brazilwood (Paubrasilia echinata) presents a significant challenge in Brazil, given its substantial value in the global production of bows for musical instruments. To address timber provenance, the use of strontium (Sr) isotope ratios as indicators of bedrock signatures has emerged as a robust tool in forensic investigations. In this study, we critically evaluate the efficacy of this approach using Sr isotope data derived from bulk soils and trees collected at two distinct sites in Brazil. Despite the statistically indistinguishable ⁸⁷Sr/⁸⁶Sr ratios observed in the investigated tree species, the compiled ⁸⁷Sr/⁸⁶Sr isotope ratios of Brazilwood from Brazilwood National Park (PNPB) and the ES Group provide valuable insights into the potential application of this method for tracing forensic timber seizures. This pilot study also addresses crucial sampling considerations.

While the regional signatures exhibit clear distinctions, the limited sample sizes underscore the necessity for supplementary methods to confidently attribute timber to a specific source forest. In isolation, this method proves most effective in refuting presumed timber provenances rather than definitively confirming them. The discussion delves into the nuances of the Sr isotope data, emphasizing the importance of increasing the number of samples and exploring complementary techniques for a more comprehensive and reliable assessment of timber origin.